ARM: 7865/1: sa1100: fix simpad compilation warning

When removing the complex GPIO interface from the SA1100 machines,
we also removed the implicit #includes for a few header files
that was included by <linux/gpio.h> thru <mach/gpio.h>, causing
a compile warning on the simpad boardfile, as <asm/irq.h> was no
longer #included, as follows:

./../arch/arm/include/asm/irq.h:9:0: warning: "NR_IRQS" redefined
[enabled by default]
 #define NR_IRQS NR_IRQS_LEGACY
 ^
In file included from ../../arch/arm/mach-sa1100/simpad.c:29:0:
../../arch/arm/mach-sa1100/include/mach/irqs.h:87:0: note: this is the
location of the previous definition
 #define NR_IRQS (IRQ_BOARD_START + NR_IRQS_LOCOMO)

This resolves the problem by explicitly including <asm/irq.h>
into the simpad boardfile.

Reported-by: Olof Johansson <olof@lixom.net>
Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Kristoffer Ericson <kristoffer.ericson@gmail.com>
Cc: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>